The present invention relates to a process for purifying exhaust gases from combustion processes and the like. The process comprises bringing exhaust gases into contact with a plurality of bubbles for an extended period of time, thus allowing scrubbing activity to take place.
The present invention also relates to an apparatus for such a process, the apparatus comprising a means for delivering exhaust gas to a bubble generator, a means of generating a plurality of bubbles, a means of conducting the thus formed bubbles to a settling tank, a means for removing impurities from the settling tank, and a means for releasing the purified gas to the atmosphere.
The process of the present invention can be described as a wet scrubbing process. Wet scrubbers employ water to clean or scrub pollutants from the air. One example of wet scrubbing technology is the use of wet scrubbers to clean smoke and other pollutants from coke plant exhaust gases. Sometimes additives are present in the water to neutralize acidity and eliminate sulfur oxides. Lime is an example of such an additive.
One problem with wet scrubbers presently employed is that the contact time between polluted air and scrubbing liquid is severely limited. Pollutants are not fully removed from the exhaust gases, resulting in return of many undesirable chemicals to the atmosphere. The present process allows for extended contact time so that all pollutants are substantially eliminated from the exhaust gases, separated from the bubble generating solution and recovered. Recovered pollutants can be recycled into useful products, or sent to proper disposal units.
The problem of cleaning contaminated air is ubiquitous. Examples of air containing chemical and/or biological pollutants are: combustion engines, power plants, garbage incinerators, coke plants, quarries, smoke stacks, flue pipes, fireplaces, clothes dryers, sewage treatment plants, and composting facilities.
U.S. Pat. No. 5,395,408 (Zeritis), filed on Oct. 12, 1993, discloses a chimney smoke scrubber which can be secured atop a chimney or flue pipe of a combustion unit. The scrubber contains a blower for drawing out the smoke and combustion gases from an enclosure, and delivering the smoke and gases under pressure to a scrubber chamber. The scrubber chamber contains an aqueous solution.
U.S. Pat. No. 5,199,362 (Carter), filed Nov. 27, 1991, relates to a pollution control system for industrial burners. The system removes harmful gases and particulates from industrial smoke streams. The smoke passes through fibrous filters and then through a liquid storage tank. The smoke then bubbles up through the liquid and reaches the surface.
U.S. Pat. No. 5,149,411 (Castle), filed Dec. 24, 1991, discloses a toxic fume scrubbing apparatus. Toxic bubbles are captured, scrubbed, and vented to a holding tank.
U.S. Pat. No. 4,393,815 (Pedersen et al), filed Aug. 15, 1980, discloses a heating plant with a smoke trap for purifying flue gas. The flue gas is drawn through a pipe and forced to bubble through a washing liquid.
U.S. Pat. No. 4,155,977 (Baker), filed Aug. 11, 1977, relates to a Pollution Control Device for an electric power generating plant. Smoke is carried from a furnace into a body of water which is contained within an enclosed concrete tank. A stainless steel grill is positioned within the tank to break up air bubbles and entrap solid particles.
None of the prior art methods hold the pollutant inside the bubble itself for an extended period of time.